%seen = (); 
    for $element (keys(%foo), keys(ēr)) { 
        $seen{$element}++; 
    } 
    @uniq = keys %seen;

    @uniq = keys %{{%foo,ēr}};

    %seen = (); 
    while (defined ($key = each %foo)) { 
        $seen{$key}++; 
    } 
    while (defined ($key = each ēr)) { 
        $seen{$key}++; 
    } 
    @uniq = keys %seen;